Photographic subbing composition having improved anchorage

Abstract

Conventional adhesive substratum compositions (e.g. subbing compositions of, for example, aqueous emulsions of a polymerized vinylidene chloride/methyl acrylate/itaconic acid terpolymer) can be used for coating dimensionally stable, hydrophobic macromolecular film bases (e.g. polyethylene terephthalate) after said base has been biaxially stretched by treating said subbing composition with an ion exchange resin.

We claim: 
     
       1. A process of coating a dimensionally stable, hydrophobic, biaxially oriented thermoplastic resin film with an aqueous emulsion of a polymer containing from 35 to 96 weight percent vinylidene chloride, from 3.5 to 64.5 weight percent of an alkyl acrylate wherein the alkyl group contains from 1 to 10 carbon atoms, an alkyl methacrylate wherein the alkyl group contains from 1 to 10 carbon atoms, acrylonitrile, methacrylonitrile, vinyl chloride, or combinations thereof and from 0.5 to 25 weight percent of a carboxylic acid containing from 3 to 10 carbon atoms and having one carbon - carbon ethylenically unsaturated double bond wherein said dispersion has an initial pH of from about 2 to about 5 and which process comprises treating said dispersion with an anionic exchange resin sufficiently to raise the pH of the dispersion to above about 7.5, applying the thus treated dispersion to the film and drying the coated dispersion. 
     
     
       2. The process of claim 1 wherein the film is a polyester containing repeating units of the structure ##STR4## wherein R is an alkylene group of from 2 to 10 carbon atoms a cycloalkylene group of from 6 to 10 carbon atoms or an arylene group of from 6 to 20 carbon atoms and Ar is either phenylene or naphthylene, which film has been biaxially oriented from 1.5 to 5X in both directions. 
     
     
       3. The process of claim 2 wherein the polyester is polyethylene terephthalate. 
     
     
       4. The process of claim 3 wherein the dispersion contains from 1 to 30 weight percent of the polymer. 
     
     
       5. The process of claim 4 wherein the dispersion is cationically exchanged prior to being anionically exchanged. 
     
     
       6. The process of claim 5 wherein the polymer in the dispersion is a sequentially polymerized mixture of (a) 60 to 90 weight percent of a terpolymer of from 35 to 90 weight percent vinylidene chloride, 3.4 to 64.5 weight percent of an alkyl acrylate wherein the alkyl group contains from 1 to 4 carbon atoms and from 0.5 to 25 weight percent of itaconic acid and (b) from 10 to 40 weight percent of a polymer, one or more acrylate esters selected from the class consisting of alkyl acrylates wherein the alkyl group contains from 1 to 10 carbon atoms and alkyl methacrylates wherein the alkyl group contains from 1 to 10 carbon atoms. 
     
     
       7. A thermoplastic, biaxially oriented hydrophobic resin film support having a subbing composition coated thereon, said composition having been anionically exchanged as an aqueous emulsion so that the pH is raised from about 2 to 5 to above about 7.5, said composition comprising 35 to 96 weight percent vinylidene chloride, 3.5 to 64.5 weight percent of an alkyl acrylate, wherein the alkyl group contains from 1 to 10 carbon atoms, an alkyl methacrylate, wherein the alkyl group contains from 1 to 10 carbon atoms, acrylonitrile, methacrylonitrile, vinyl chloride, or mixtures thereof, and 0.5 to 25 weight percent of a carboxylic acid containing 3 to 10 carbon atoms and having at least one carbon to carbon ethylenically unsaturated double bond. 
     
     
       8. The article of claim 7 wherein said resin film support is polyethylene terephthalate. 
     
     
       9. The article of claim 7 wherein an organic acid and a wetting agent are added to the anionically-exchanged subbing composition. 
     
     
       10. The article of claim 9 wherein the organic acid is malonic acid and the wetting agent is sodium myristyl either sulfate.